Tissue expansion devices have been used by plastic surgeons for over thirty years for the generation of skin flaps in reconstructive surgery. Skin expansion is commonly observed, for example, in pregnant women. For the overlying skin to remain healthy, the expansion must take place gradually as in the case of the developing fetus. Additionally, the underlying pressure on the skin must be distributed uniformly to prevent necrosis of the thin overlying tissue. These considerations have guided the development of the tissue expansion devices currently in use.
It is particularly desirable to generate a donor skin flap on a portion of the body contiguous with the recipient area. In this way, skin texture and abundance of hair in the grafted area can be made to more or less blend with the surrounding skin giving a more esthetically pleasing result. To accomplish this, the surgeon makes a pocket under the skin and subcutaneous tissue adjacent to the area to be grafted. A tissue expander is placed in the pocket and gradually inflated over a period of weeks or months until the device is fully inflated. Since the base of most tissue expanders is thicker and less flexible than the cover, the envelope presses upward during expansion stretching the overlying skin. As the skin stretches, it becomes thinner and more vulnerable to trauma. In particular, if the underlying pressure on such distended skin is excessive, circulation may be impaired with resulting necrosis and death of cells.
Due to the tension on the periphery of the base of conventional tissue expanders caused by the upward pull of the expanded flexible cover, the edges of the base can curl up when the device is fully expanded or over-expanded. If the base curls up, it can cause excessive pressure on the thin overlying skin which can result in necrosis and erosion. It is the object of the present invention to provide a tissue expander with a base that protects the overlying tissue against damage associated with base pressure observed with fully inflated or over-inflated current art devices.